Thursday-Sunday 4/13-4/16

Issued: Thu, Apr 13, 2017 at 8AM

Expires: Sun, Apr 16, 2017

Spring conditions are in full swing:

Low avalanche danger in the morning….Considerable danger in the afternoon with rising temperatures and solar warming!

Areas protected from wind and lower in elevation will be more susceptible to warming and avalanche hazard.

Intense snow transport yesterday was flagging off peaks and drifting into fresh wind slabs that are likely sensitive.

As the sun warms and weaken snow on steep southerly faces, plan your day appropriately….limiting exposure to avalanches from above. Wet avalanches can run much farther than expected.

Friday April 14: VAC Full Moon Spring Fling FUNraiser with Acoustic Avalanche at the Tsaina Lodge.   Grab a date and come boogie! Fire dancing, DJ and raffle too!

Above 2,500ft Considerable

1,800 to 2,500ft Considerable

Below 1,800ft Considerable

Degrees of Avalanche Danger ?

1. Low
2. Moderate
3. Considerable
4. High
5. Extreme

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

THURSDAY FRIDAY SATURDAY & SUNDAY

DANGER SCALE

 

WET AVALANCHES:
Elevation:
   Below 5000′
Aspect:
   East in AM, bearing South, then West in PM
Terrain:
Steep terrain near rocks and vegetation.
Sensitivity:
   Touchy when warmed.
Distribution:
   Specific.
Likelihood (Human Triggered):
  Possible
Size:
  Small-Large
Danger Trend:
   Increasing quickly each day with warming temperatures, falling at night
Forecaster Confidence:
   Good

WIND SLAB:
Elevation:
   Above 3000′
Aspect:
   Southerlies
Terrain:
Near ridgelines, rollovers and gully walls.
Sensitivity:
   Responsive to Touchy when sitting on sun crust.
Distribution:
   Specific.
Likelihood (Human Triggered):
  Possible
Size:
  Small
Danger Trend:
   Increasing.
Forecaster Confidence:
   Fair

PERSISTENT SLAB:
Elevation:
  Above 2500′
Aspect:
 All
Terrain:
Slopes > 35*
Sensitivity:
   Stubborn on northerlies, Touchy when warmed by sun
Distribution:
   Widespread
Likelihood (Human Triggered):
   Possible
Size:
  Small – Large
Danger Trend:
   Decreasing
Forecaster Confidence:
   Fair

AVALANCHE PROBLEM SCALE DESCRIPTORS:
Sensitivity: Non-reactive, Stubborn, Responsive, Touchy
Distribution: Isolated, Specific, Widespread
Likelihood: Unlikely, Possible, Likely, Nearly Certain
Size: Small, Large, Very Large (size scale <here>)
Danger Trend: Increasing, Steady, Decreasing
Forecaster Confidence: Good, Fair, Poor

AVALANCHE PROBLEM TOOLBOX <here>

SNOWPACK DISCUSSION:

Maritime (Coastal) Specific: 

Winds have been consistently strong out of the NE and have been moving the recent soft snow to southerly aspects, sometimes resting on sun crust and triggering easily. As these winds die down Friday, expect the solar radiation to be more impactful on exposed slopes at higher elevations that have been cooled as of late.

Dig and look for buried surface hoar that was found all the way up to ridgeline. Seen still standing under new snow near the summit of Girls Mountain.

The most recent storm produced 3-4 feet of new snow above 4500′ (rain below) in the costal region of Valdez. The new snow has settled to 1-2 feet of medium density powder.

There have been reports of the afternoon sun triggering natural avalanches. The first type being wet avalanches which have the potential to slide to the ground. They are most likely to be triggered on southerly aspects especially in elevations below 5000′ when temperatures reach above 32 degrees. The second type being dry slab avalanches consisting of the most recent snowfall. These avalanches are possible on all aspects other than south, realistically anywhere dry powder snow can be found. The warmer temperatures in the afternoon will certainly increase the chances of triggering a slide. 

Sharing your observations creates an informed community that everyone benefits from at some point.

Recent Avalanche Activity

Maritime (Coastal) Specific:

  • April 12: Numerous natural, wet loose avalanches to size D2.5 from Marshall Pass to the port, large running slides down the south faces west of Mineral creek to the flats/sea level. Many running to ground with dirty debris.
  • April 11: With more direct sun, more wet loose releasing out of steep, south aspects entraining snow to D2.5, sometimes to ground
  • April 7: new natural west aspect in the Books.

      Photo: Bobby Lieberman
  • April 6-8: many wet loose avalanches on south aspects 4500′ and below stepped down and pulled out the last storm slab to old firm surfaces. These large size D3 avalanches ran full path. A few reports of similar activity above 4500′.

Large wet debris running far into flats on south side of Tone’s Temple

Slabs pulling out from wet loose off of southerlies along Worthington Glacier

More fresh releases off Girls Mountain south face.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  21 / 35
Ridgetop Wind Forecast (direction/mph):  NE / 20-45
Snowfall (in/water equivalent):  0″ / 0″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction  6 / Var  30 / NE
Max Wind Gust (mph) / Direction  22 / SE  43 / NE
Temperature Min / Max (*F)  46 / 55  30 / 39

Weather Forecast:     Warm temperatures persist, as it is 5 degrees and 10 degrees warmer this morning than 24 hours ago at Thompson Pass and the upper Tsaina River respectively. It felt balmy in town yesterday and waterfalls were plunging into Duck Flats in the early evening. Strong winds continue out of the north into late tonight. Clear skies will make for beautiful days into Saturday, when some high clouds may squeeze into our area and stick around until Sunday when it will clear again. No moisture in the forecast.

Additional Info & Media

SNOW HISTORY: Valdez 4/13 AM Thompson Pass 4/13 AM
24 Hour Snow / Water Equiv.  0”/0.0″ 0″ /0″
Storm Snow /Water Equiv. (3/27-4/6)  16.9″ /4.1″ 24″ /2.4″
Current Snow Depth 30″ 42″
April Snow / Water Equiv. ~″ /1.82″ 8″ / 0.8″
Total Winter Snowfall / Water Equiv. 239.8″ /24.47” 327″ / 31.4″
Snowload in Valdez 65.0 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (4/13 AM)/STORM TOTAL (3/27-4/6)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 0″ / ~16″ / ?”
Upper Tsaina at 1750 ft (in): 0″ / ?” / 1.2+”
Sugarloaf at 550 ft (in): 0″/ 20+rain” / 2.8″
SNOW DEPTH & WATER SURVEY (4/2/2017) Depth Snow Water Equivalent
Milepost 2.5 Valdez  41.9″  11.9″
Milepost 18 40″ 11.9″
Milepost 29 Worthington Flats 62.2″ 19.6″
Milepost 37 Tsaina River bridge 46.3″ 12.5″
This survey is done the first week of each month.

Weather Quicklinks:

SNOW CLIMATE ZONES:

  • coastal-zone-iconMaritime (Coastal) – from the Port of Valdez to Thompson Pass, all waters flowing into Valdez Arm and everything south of Marshall Pass.
  • intermountain-zone-iconInter-mountain (Transitional) – between Thompson Pass and Rendezvous Lodge.
  • interior-zone-iconContinental (Interior) – the dry north side of the Chugach (north of 46 Mile, including the Tonsina River).

Photo of Thompson Pass

thompson-pass-ski-runs

Interactive Map of Valdez Forecast Areas w/ Many Resource Layers (Trevor Grams)

climate-zones-topoclimate-zones-satellitegoogle-earth1

Run Map of Thompson Pass Area (Sean Wisner) (2MB download)
VAC Run Map Thompson Pass

NEWS: Our region is “one of the snowiest places on earth” – Serendipity / Rendezvous snowfall record set in 1963 <here>.

Free smart phone avalanche forecasts at: http://www.avalancheforecasts.com/

Posted in Maritime Forecasts.

Forecaster: Kevin Salys